Modelling shared attention through relational reinforcement learning

Shared attention is a type of communication very important among human beings. It is sometimes reserved for the more complex form of communication being constituted by a sequence of four steps: mutual gaze, gaze following, imperative pointing and declarative pointing. Some approaches have been proposed in Human-Robot Interaction area to solve part of shared attention process, that is, the most of works proposed try to solve the first two steps. Models based on temporal difference, neural networks, probabilistic and reinforcement learning are methods used in several works. In this article, we are presenting a robotic architecture that provides a robot or agent, the capacity of learning mutual gaze, gaze following and declarative pointing using a robotic head interacting with a caregiver. Three learning methods have been incorporated to this architecture and a comparison of their performance has been done to find the most adequate to be used in real experiment. The learning capabilities of this architecture have been analyzed by observing the robot interacting with the human in a controlled environment. The experimental results show that the robotic head is able to produce appropriate behavior and to learn from sociable interaction.

Specification, execution and verification of interaction protocols: an approach based on computational logic

Interaction protocols establish how different computational entities can interact with each other. The interaction can be finalized to the exchange of data, as in 'communication protocols', or can be oriented to achieve some result, as in 'application protocols'. Moreover, with the increasing complexity of modern distributed systems, protocols are used also to control such a complexity, and to ensure that the system as a whole evolves with certain features. However, the extensive use of protocols has raised some issues, from the language for specifying them to the several verification aspects. Computational Logic provides models, languages and tools that can be effectively adopted to address such issues: its declarative nature can be exploited for a protocol specification language, while its operational counterpart can be used to reason upon such specifications. In this thesis we propose a proof-theoretic framework, called SCIFF, together with its extensions. SCIFF is based on Abductive Logic Programming, and provides a formal specification language with a clear declarative semantics (based on abduction). The operational counterpart is given by a proof procedure, that allows to reason upon the specifications and to test the conformance of given interactions w.r.t. a defined protocol. Moreover, by suitably adapting the SCIFF Framework, we propose solutions for addressing (1) the protocol properties verification (g-SCIFF Framework), and (2) the a-priori conformance verification of peers w.r.t. the given protocol (AlLoWS Framework). We introduce also an agent based architecture, the SCIFF Agent Platform, where the same protocol specification can be used to program and to ease the implementation task of the interacting peers.

Interactions between normative systems and software cognitive agents. A formalization in temporal modal defeasible logic and its implementation

Sustainable computer systems require some flexibility to adapt to environmental unpredictable changes. A solution lies in autonomous software agents which can adapt autonomously to their environments. Though autonomy allows agents to decide which behavior to adopt, a disadvantage is a lack of control, and as a side effect even untrustworthiness: we want to keep some control over such autonomous agents. How to control autonomous agents while respecting their autonomy? A solution is to regulate agents’ behavior by norms. The normative paradigm makes it possible to control autonomous agents while respecting their autonomy, limiting untrustworthiness and augmenting system compliance. It can also facilitate the design of the system, for example, by regulating the coordination among agents. However, an autonomous agent will follow norms or violate them in some conditions. What are the conditions in which a norm is binding upon an agent? While autonomy is regarded as the driving force behind the normative paradigm, cognitive agents provide a basis for modeling the bindingness of norms. In order to cope with the complexity of the modeling of cognitive agents and normative bindingness, we adopt an intentional stance. Since agents are embedded into a dynamic environment, things may not pass at the same instant. Accordingly, our cognitive model is extended to account for some temporal aspects. Special attention is given to the temporal peculiarities of the legal domain such as, among others, the time in force and the time in efficacy of provisions. Some types of normative modifications are also discussed in the framework. It is noteworthy that our temporal account of legal reasoning is integrated to our commonsense temporal account of cognition. As our intention is to build sustainable reasoning systems running unpredictable environment, we adopt a declarative representation of knowledge. A declarative representation of norms will make it easier to update their system representation, thus facilitating system maintenance; and to improve system transparency, thus easing system governance. Since agents are bounded and are embedded into unpredictable environments, and since conflicts may appear amongst mental states and norms, agent reasoning has to be defeasible, i.e. new pieces of information can invalidate formerly derivable conclusions. In this dissertation, our model is formalized into a non-monotonic logic, namely into a temporal modal defeasible logic, in order to account for the interactions between normative systems and software cognitive agents.

Constraint handling rules. Compositional semantics and program transformation

This thesis intends to investigate two aspects of Constraint Handling Rules (CHR). It proposes a compositional semantics and a technique for program transformation. CHR is a concurrent committed-choice constraint logic programming language consisting of guarded rules, which transform multi-sets of atomic formulas (constraints) into simpler ones until exhaustion [Frü06] and it belongs to the declarative languages family. It was initially designed for writing constraint solvers but it has recently also proven to be a general purpose language, being as it is Turing equivalent [SSD05a]. Compositionality is the first CHR aspect to be considered. A trace based compositional semantics for CHR was previously defined in [DGM05]. The reference operational semantics for such a compositional model was the original operational semantics for CHR which, due to the propagation rule, admits trivial non-termination. In this thesis we extend the work of [DGM05] by introducing a more refined trace based compositional semantics which also includes the history. The use of history is a well-known technique in CHR which permits us to trace the application of propagation rules and consequently it permits trivial non-termination avoidance [Abd97, DSGdlBH04]. Naturally, the reference operational semantics, of our new compositional one, uses history to avoid trivial non-termination too. Program transformation is the second CHR aspect to be considered, with particular regard to the unfolding technique. Said technique is an appealing approach which allows us to optimize a given program and in more detail to improve run-time efficiency or spaceconsumption. Essentially it consists of a sequence of syntactic program manipulations which preserve a kind of semantic equivalence called qualified answer [Frü98], between the original program and the transformed ones. The unfolding technique is one of the basic operations which is used by most program transformation systems. It consists in the replacement of a procedure-call by its definition. In CHR every conjunction of constraints can be considered as a procedure-call, every CHR rule can be considered as a procedure and the body of said rule represents the definition of the call. While there is a large body of literature on transformation and unfolding of sequential programs, very few papers have addressed this issue for concurrent languages. We define an unfolding rule, show its correctness and discuss some conditions in which it can be used to delete an unfolded rule while preserving the meaning of the original program. Finally, confluence and termination maintenance between the original and transformed programs are shown. This thesis is organized in the following manner. Chapter 1 gives some general notion about CHR. Section 1.1 outlines the history of programming languages with particular attention to CHR and related languages. Then, Section 1.2 introduces CHR using examples. Section 1.3 gives some preliminaries which will be used during the thesis. Subsequentely, Section 1.4 introduces the syntax and the operational and declarative semantics for the first CHR language proposed. Finally, the methodologies to solve the problem of trivial non-termination related to propagation rules are discussed in Section 1.5. Chapter 2 introduces a compositional semantics for CHR where the propagation rules are considered. In particular, Section 2.1 contains the definition of the semantics. Hence, Section 2.2 presents the compositionality results. Afterwards Section 2.3 expounds upon the correctness results. Chapter 3 presents a particular program transformation known as unfolding. This transformation needs a particular syntax called annotated which is introduced in Section 3.1 and its related modified operational semantics !0t is presented in Section 3.2. Subsequently, Section 3.3 defines the unfolding rule and prove its correctness. Then, in Section 3.4 the problems related to the replacement of a rule by its unfolded version are discussed and this in turn gives a correctness condition which holds for a specific class of rules. Section 3.5 proves that confluence and termination are preserved by the program modifications introduced. Finally, Chapter 4 concludes by discussing related works and directions for future work.

L'influenza del sonno sull'andamento temporale della consolidazione delle abilità procedurali

Background: It is well known, since the pioneristic observation by Jenkins and Dallenbach (Am J Psychol 1924;35:605-12), that a period of sleep provides a specific advantage for the consolidation of newly acquired informations. Recent research about the possible enhancing effect of sleep on memory consolidation has focused on procedural memory (part of non-declarative memory system, according to Squire’s taxonomy), as it appears the memory sub-system for which the available data are more consistent. The acquisition of a procedural skill follows a typical time course, consisting in a substantial practice-dependent learning followed by a slow, off-line improvement. Sleep seems to play a critical role in promoting the process of slow learning, by consolidating memory traces and making them more stable and resistant to interferences. If sleep is critical for the consolidation of a procedural skill, then an alteration of the organization of sleep should result in a less effective consolidation, and therefore in a reduced memory performance. Such alteration can be experimentally induced, as in a deprivation protocol, or it can be naturally observed in some sleep disorders as, for example, in narcolepsy. In this research, a group of narcoleptic patients, and a group of matched healthy controls, were tested in two different procedural abilities, in order to better define the size and time course of sleep contribution to memory consolidation. Experimental Procedure: A Texture Discrimination Task (Karni & Sagi, Nature 1993;365:250-2) and a Finger Tapping Task (Walker et al., Neuron 2002;35:205-11) were administered to two indipendent samples of drug-naive patients with first-diagnosed narcolepsy with cataplexy (International Classification of Sleep Disorder 2nd ed., 2005), and two samples of matched healthy controls. In the Texture Discrimination task, subjects (n=22) had to learn to recognize a complex visual array on the screen of a personal computer, while in the Finger Tapping task (n=14) they had to press a numeric sequence on a standard keyboard, as quickly and accurately as possible. Three subsequent experimental sessions were scheduled for each partecipant, namely a training session, a first retrieval session the next day, and a second retrieval session one week later. To test for possible circadian effects on learning, half of the subjects performed the training session at 11 a.m. and half at 17 p.m. Performance at training session was taken as a measure of the practice-dependent learning, while performance of subsequent sessions were taken as a measure of the consolidation level achieved respectively after one and seven nights of sleep. Between training and first retrieval session, all participants spent a night in a sleep laboratory and underwent a polygraphic recording. Results and Discussion: In both experimental tasks, while healthy controls improved their performance after one night of undisturbed sleep, narcoleptic patients showed a non statistically significant learning. Despite this, at the second retrieval session either healthy controls and narcoleptics improved their skills. Narcoleptics improved relatively more than controls between first and second retrieval session in the texture discrimination ability, while their performance remained largely lower in the motor (FTT) ability. Sleep parameters showed a grater fragmentation in the sleep of the pathological group, and a different distribution of Stage 1 and 2 NREM sleep in the two groups, being thus consistent with the hypothesis of a lower consolidation power of sleep in narcoleptic patients. Moreover, REM density of the first part of the night of healthy subjects showed a significant correlation with the amount of improvement achieved at the first retrieval session in TDT task, supporting the hypothesis that REM sleep plays an important role in the consolidation of visuo-perceptual skills. Taken together, these results speak in favor of a slower, rather than lower consolidation of procedural skills in narcoleptic patients. Finally, an explanation of the results, based on the possible role of sleep in contrasting the interference provided by task repetition is proposed.

XCSurf: Riprogettazione dell'Interfaccia Utente

Il Progetto XCModel, che da dieci anni si sviluppa e si perfeziona col contributo di varie persone, consente la progettazione di scene 3D e la resa fotorealistica. Esso si appoggia sulle funzionalita' grafiche di X-Window in Linux: si tratta di un ambiente in costante evoluzione, dovuta sia alle continue innovazioni hardware che ai cambiamenti degli standard. XCModel e' composto da vari pacchetti, ognuno dei quali specializzato nel trattare un particolare aspetto della modellazione o della resa (curve, superfici, textures, luci, ...) e che si presentano come applicazioni dotate di una sofisticata interfaccia grafica. Tutte attingono alle funzioni della Libreria XTools, che fornisce numerose primitive grafiche facenti uso delle potenzialita' di X-Window. I recenti cambiamenti nelle specifiche di X-Org, ed in particolare la de- standardizzazione del backing-store, ha obbligato il team di XCModel ad una consistente riprogettazione di XTools e di tutti i pacchetti che su di esso s'appoggiano. S'e' colta l'occasione per un massiccio debugging e per modificare i pacchetti in base alle impressioni emerse nel corso degli anni da parte degli utilizzatori, primi tra tutti gli studenti del corso di Grafica tenuto dal Prof. Giulio Casciola, project-manager di XCModel: questa e' un'ulteriore testimonianza del continuo adattamento e dell'aggiornabilita' del Progetto! Nella fattispecie, ci si occupera' delle modifiche effettuate in particolare al pacchetto XCSurf, finalizzato alla creazione ed alla modifica di curve e superfici 3D da utilizzarsi successivamente per la creazione delle scene: tale pacchetto e' di fatto risultato il pie' avulso dalle specifiche di XTools, il che ha costretto ad un massiccio intervento al codice del programma, ma d'altro canto ha consentito una standardizzazione del pacchetto in linea con gli altri, in particolare ridisegnandone l'interfaccia. Nel primo capitolo si effettuera' una veloce panoramica dell'ambiente XCModel e delle problematiche emerse dai cambiamenti degli standard di X-Window. Il secondo capitolo affrontera' un'ampia analisi dell'hardware, del software e dei paradigmi che caratterizzano la grafica interattiva, e gli ambienti necessari per interagire con essa ed esaminando i vari obiettivi raggiungibili. Infine, il terzo capitolo analizzera' nel dettaglio le modifiche effettuate ai pacchetti di XCModel ed in particolare ad XCSurf per l'adattamento ai nuovi standard, nel rispetto delle politiche e delle linee guida dettate dalla grafica interattiva.

Costrutti ed Applicazioni di Programmazione Generica in Linguaggi Object-Oriented

Generic programming is likely to become a new challenge for a critical mass of developers. Therefore, it is crucial to refine the support for generic programming in mainstream Object-Oriented languages — both at the design and at the implementation level — as well as to suggest novel ways to exploit the additional degree of expressiveness made available by genericity. This study is meant to provide a contribution towards bringing Java genericity to a more mature stage with respect to mainstream programming practice, by increasing the effectiveness of its implementation, and by revealing its full expressive power in real world scenario. With respect to the current research setting, the main contribution of the thesis is twofold. First, we propose a revised implementation for Java generics that greatly increases the expressiveness of the Java platform by adding reification support for generic types. Secondly, we show how Java genericity can be leveraged in a real world case-study in the context of the multi-paradigm language integration. Several approaches have been proposed in order to overcome the lack of reification of generic types in the Java programming language. Existing approaches tackle the problem of reification of generic types by defining new translation techniques which would allow for a runtime representation of generics and wildcards. Unfortunately most approaches suffer from several problems: heterogeneous translations are known to be problematic when considering reification of generic methods and wildcards. On the other hand, more sophisticated techniques requiring changes in the Java runtime, supports reified generics through a true language extension (where clauses) so that backward compatibility is compromised. In this thesis we develop a sophisticated type-passing technique for addressing the problem of reification of generic types in the Java programming language; this approach — first pioneered by the so called EGO translator — is here turned into a full-blown solution which reifies generic types inside the Java Virtual Machine (JVM) itself, thus overcoming both performance penalties and compatibility issues of the original EGO translator. Java-Prolog integration Integrating Object-Oriented and declarative programming has been the subject of several researches and corresponding technologies. Such proposals come in two flavours, either attempting at joining the two paradigms, or simply providing an interface library for accessing Prolog declarative features from a mainstream Object-Oriented languages such as Java. Both solutions have however drawbacks: in the case of hybrid languages featuring both Object-Oriented and logic traits, such resulting language is typically too complex, thus making mainstream application development an harder task; in the case of library-based integration approaches there is no true language integration, and some “boilerplate code” has to be implemented to fix the paradigm mismatch. In this thesis we develop a framework called PatJ which promotes seamless exploitation of Prolog programming in Java. A sophisticated usage of generics/wildcards allows to define a precise mapping between Object-Oriented and declarative features. PatJ defines a hierarchy of classes where the bidirectional semantics of Prolog terms is modelled directly at the level of the Java generic type-system.

Semplificare l'interazione con l'utente nell'interprete IntML

Si presenta IntML, un linguaggio funzionale di recente introduzione che rende possibile la comunicazione bidirezionale; si descrive il funzionamento del suo interprete, a cui abbiamo aggiunto nuove funzionalita' che semplificano le operazioni di debugging e testing degli algoritmi.

Theoretical and implementation aspects in the mechanization of the metatheory of programming languages

Interactive theorem provers are tools designed for the certification of formal proofs developed by means of man-machine collaboration. Formal proofs obtained in this way cover a large variety of logical theories, ranging from the branches of mainstream mathematics, to the field of software verification. The border between these two worlds is marked by results in theoretical computer science and proofs related to the metatheory of programming languages. This last field, which is an obvious application of interactive theorem proving, poses nonetheless a serious challenge to the users of such tools, due both to the particularly structured way in which these proofs are constructed, and to difficulties related to the management of notions typical of programming languages like variable binding. This thesis is composed of two parts, discussing our experience in the development of the Matita interactive theorem prover and its use in the mechanization of the metatheory of programming languages. More specifically, part I covers: - the results of our effort in providing a better framework for the development of tactics for Matita, in order to make their implementation and debugging easier, also resulting in a much clearer code; - a discussion of the implementation of two tactics, providing infrastructure for the unification of constructor forms and the inversion of inductive predicates; we point out interactions between induction and inversion and provide an advancement over the state of the art. In the second part of the thesis, we focus on aspects related to the formalization of programming languages. We describe two works of ours: - a discussion of basic issues we encountered in our formalizations of part 1A of the Poplmark challenge, where we apply the extended inversion principles we implemented for Matita; - a formalization of an algebraic logical framework, posing more complex challenges, including multiple binding and a form of hereditary substitution; this work adopts, for the encoding of binding, an extension of Masahiko Sato's canonical locally named representation we designed during our visit to the Laboratory for Foundations of Computer Science at the University of Edinburgh, under the supervision of Randy Pollack.

Oswald Mathias Ungers: Belvederestraße 60. Zu einer neuen Archtektur.

La presente Tesi di Dottorato intende affrontare una lettura critica della Casa in Belvederestraße 60, realizzata dall’architetto Oswald Mathias Ungers (Kaisersesch, 12 luglio 1926 – Köln, 30 settembre 2007), nel 1958-’59 a Köln-Müngersdorf, come studio per sé ed abitazione per la propria famiglia. Questo primo oggetto della ricerca viene considerato evidente espressione delle convinzioni formali e compositive dell’architetto, negli anni Cinquanta e Sessanta. A differenza di altri progetti residenziali coevi ed antecedenti, frutto di un’elaborazione autonoma, la prima casa che costruisce per sé riflette una maggiore libertà di pensiero, dettata dalla coincidenza delle figure di progettista e committente; a ciò si aggiunge anche una precisa volontà dichiarativa ed ideologica. Proprio quest’ultimo aspetto permette di introdurre il secondo oggetto della Tesi: il manifesto “ideologico”, Zu einer neuen Architektur, scritto dallo stesso Oswald Mathias Ungers e da Reinhard Gieselmann, alla fine del 1960; un breve testo che espone, con toni perentori ed inappellabili, il punto di vista dei due architetti nei confronti di un panorama architettonico e critico, caratterizzato da una sterilità di pensiero dilagante, a causa dell’egemonia costruttiva funzionalista. La ricerca indaga quindi le forti reciprocità delle due opere: casa e testo, viste in chiave di “manifesto scritto e manifesto costruito”. Il primo legame tra i due soggetti è senza dubbio la concomitanza temporale, (tra il 1958 ed il 1960) associata ad un rapporto causa-effetto, tale per cui il manifesto viene redatto a difesa delle aspre critiche scaturite dalla pubblicazione della casa sulla rivista Bauwelt. Il secondo nesso è la possibilità di comprendere le accezioni effettive dei termini impiegati nella redazione del testo, attraverso le forme di una delle opere maggiormente personali dell’architetto, estraendone il senso e conferendogli un’immagine architettonica. Si vuole creare così un rapporto biunivoco di traducibilità, dell’architettura nello scritto e della semantica ungersiana in azioni compositive.

Studio di modelli di illuminazione e texture in ambiente WebGL

Il mondo di Internet ha vissuto un radicale e inarrestabile processo di rinnovamento nel corso dell'ultimo decennio. Nel giro di pochi anni, i siti che popolano il World Wide Web si sono evoluti divenendo vere e proprie applicazioni in grado di fornire un livello di interattività e di coinvolgimento fino ad allora impensabile. Il mondo del Web è mutato, e con esso quello dei browser, i quali assumono sempre più le conformazioni di "sistemi operativi nei sistemi operativi": si sono tramutati in complesse piattaforme di sviluppo in grado di fornire a programmatori e web designer potenti librerie e API relative a qualsiasi ambito, nonché avanzati strumenti di debugging. Numerosi standard che governano l'ecosistema di Internet hanno raggiunto la maturità in questo contesto: fra tutti HTML5, il quale ha arricchito enormemente le potenzialità di un browser introducendo nuovi strumenti orientati alla multimedialità e alla classificazione semantica delle risorse. Altri standard altrettanto importanti hanno visto la luce in questi anni, affermandosi e conquistando, nel giro di pochissimi anni, l'interesse di un'ampia platea di sviluppatori. E' il caso di WebGL, una potente e flessibile libreria grafica derivata dal mondo di OpenGL che ha aperto le porte al rendering di scene tridimensionali all'interno di un qualsiasi browser moderno. WebGL ha rappresentato un punto di svolta abbattendo un'ulteriore barriera tra il mondo del web che vive all'interno di un browser e la dimensione delle applicazioni native che popolano un sistema operativo, consolidando il già affermato concetto di web app che lentamente sta seppellendo l'idea di "sito" così come era stato concepito all'inizio del nuovo millennio. Scopo di questo elaborato è quello di fornire una panoramica delle principali funzionalità offerte dalla libreria WebGL (con una particolare attenzione per il supporto cross browser) e di analizzare le possibilità che essa offre, studiando e implementando i principali modelli di illuminazione e le tecniche di applicazione texture per definire un ambiente tridimensionale esplorabile e il più possibile realistico all'interno della dimensione del web.

Firmware development and testing for L1/L2 IBL upgrade

Il lavoro di questa tesi riguarda principalmente l'upgrade, la simulazione e il test di schede VME chiamate ReadOut Driver (ROD), che sono parte della catena di elaborazione ed acquisizione dati di IBL (Insertable B-Layer). IBL è il nuovo componente del Pixel Detector dell'esperimento ATLAS al Cern che è stato inserito nel detector durante lo shut down di LHC; fino al 2012 infatti il Pixel Detector era costituito da tre layer, chiamati (partendo dal più interno): Barrel Layer 0, Layer 1 e Layer 2. Tuttavia, l'aumento di luminosità di LHC, l'invecchiamento dei pixel e la richiesta di avere misure sempre più precise, portarono alla necessità di migliorare il rivelatore. Così, a partire dall'inizio del 2013, IBL (che fino a quel momento era stato un progetto sviluppato e finanziato separatamente dal Pixel Detector) è diventato parte del Pixel Detector di ATLAS ed è stato installato tra la beam-pipe e il layer B0. Questa tesi fornirà innanzitutto una panoramica generale dell'esperimento ATLAS al CERN, includendo aspetti sia fisici sia tecnici, poi tratterà in dettaglio le varie parti del rivelatore, con particolare attenzione su Insertable B-Layer. Su quest'ultimo punto la tesi si focalizzerà sui motivi che ne hanno portato alla costruzione, sugli aspetti di design, sulle tecnologie utilizzate (volte a rendere nel miglior modo possibile compatibili IBL e il resto del Pixel Detector) e sulle scelte di sviluppo e fabbricazione. La tesi tratterà poi la catena di read-out dei dati, descrivendo le tecniche di interfacciamento con i chip di front-end, ed in particolare si concentrerà sul lavoro svolto per l'upgrade e lo sviluppo delle schede ReadOut Drivers (ROD) introducendo le migliorie da me apportate, volte a eliminare eventuali difetti, migliorare le prestazioni ed a predisporre il sistema ad una analisi prestazionale del rivelatore. Allo stato attuale le schede sono state prodotte e montate e sono già parte del sistema di acquisizione dati del Pixel Detector di ATLAS, ma il firmware è in continuo aggiornamento. Il mio lavoro si è principalmente focalizzato sul debugging e il miglioramento delle schede ROD; in particolare ho aggiunto due features: - programmazione parallela delle FPGA} delle ROD via VME. IBL richiede l'utilizzo di 15 schede ROD e programmandole tutte insieme (invece che una alla volta) porta ad un sensibile guadagno nei tempi di programmazione. Questo è utile soprattutto in fase di test; - reset del Phase-Locked Loop (PLL)} tramite VME. Il PLL è un chip presente nelle ROD che distribuisce il clock a tutte le componenti della scheda. Avere la possibilità di resettare questo chip da remoto permette di risolvere problemi di sincronizzazione. Le ReadOut Driver saranno inoltre utilizzate da più layer del Pixel Detector. Infatti oltre ad IBL anche i dati provenienti dai layer 1 e 2 dei sensori a pixel dell’esperimento ATLAS verranno acquisiti sfruttando la catena hardware progettata, realizzata e testata a Bologna.

Semantic memory involvement in the default mode network: a functional neuroimaging study using independent component analysis

The Default Mode Network (DMN) is a higher order functional neural network that displays activation during passive rest and deactivation during many types of cognitive tasks. Accordingly, the DMN is viewed to represent the neural correlate of internally-generated self-referential cognition. This hypothesis implies that the DMN requires the involvement of cognitive processes, like declarative memory. The present study thus examines the spatial and functional convergence of the DMN and the semantic memory system. Using an active block-design functional Magnetic Resonance Imaging (fMRI) paradigm and Independent Component Analysis (ICA), we trace the DMN and fMRI signal changes evoked by semantic, phonological and perceptual decision tasks upon visually-presented words. Our findings show less deactivation during semantic compared to the two non-semantic tasks for the entire DMN unit and within left-hemispheric DMN regions, i.e., the dorsal medial prefrontal cortex, the anterior cingulate cortex, the retrosplenial cortex, the angular gyrus, the middle temporal gyrus and the anterior temporal region, as well as the right cerebellum. These results demonstrate that well-known semantic regions are spatially and functionally involved in the DMN. The present study further supports the hypothesis of the DMN as an internal mentation system that involves declarative memory functions.

Immediate Search in the IDE as an Example of Socio-Technical Congruence in Search-Driven Development

Search-driven development is mainly concerned with code reuse but also with code navigation and debugging. In this essay we look at search-driven navigation in the IDE. We consider Smalltalk-80 as an example of a programming system with search-driven navigation capabilities and explore its human factors. We present how immediate search results lead to a user experience of code browsing rather than one of waiting for and clicking through search results. We explore the socio-technical congruence of immediate search, ie unification of tasks and breakpoints with method calls, which leads to simpler and more extensible development tools. Eventually we conclude with remarks on the socio-technical congruence of search-driven development.

Pinocchio: Bringing Reflection to Life with First-Class Interpreters

To support development tools like debuggers, runtime systems need to provide a meta-programming interface to alter their semantics and access internal data. Reflective capabilities are typically fixed by the Virtual Machine (VM). Unanticipated reflective features must either be simulated by complex program transformations, or they require the development of a specially tailored VM. We propose a novel approach to behavioral reflection that eliminates the barrier between applications and the VM by manipulating an explicit tower of first-class interpreters. Pinocchio is a proof-of-concept implementation of our approach which enables radical changes to the interpretation of programs by explicitly instantiating subclasses of the base interpreter. We illustrate the design of Pinocchio through non-trivial examples that extend runtime semantics to support debugging, parallel debugging, and back-in-time object-flow debugging. Although performance is not yet addressed, we also discuss numerous opportunities for optimization, which we believe will lead to a practical approach to behavioral reflection.